Here's what we can say with just a few games left in Major League Baseball's regular season. The Boston Red Sox and Houston Astros are scary good. The New York Yankees are not far behind. And the Oakland A's have confounded everyone again by being great when they should be terrible. And in the National League, well, no one can figure that out yet. But to help us out, we have Jonah Keri of CBS Sports. Welcome to the program.

JONAH KERI: Thanks for having me.

CORNISH: So the Red Sox were at one point forcing experts to wonder if this team could be the best ever. Then they've slowed down a bit, right? So now we're wondering if they're merely one of the best. It seems ridiculous to ask if the team that's won 106 games is vulnerable in the playoffs. But is that the case?

KERI: Well, they actually might be because if you look at this team, they do have the likely most valuable player in the league - Mookie Betts. He's been excellent. They have J.D. Martinez, who for a while was making a run at the Triple Crown which is a very, very rare feat in baseball - and just a loaded offense. The issue is the starting rotation.

So if you look at their top two starters - or arguably their top two starters - one is Chris Sale, terrific lefthander. He's always very good. But the problem is he spent time on the disabled list this year, and he's just now ramping up his workload. So they don't know how many innings he'll be able to give them in the postseason. That's one.

And then two is David Price, who's one of the biggest enigmas in all of baseball. He's got to $217 million contract - very good in the regular season typically. And the postseason, he's awful. Both he and Chris Sale will need to prove themselves. Otherwise, given that the Yankees and Astros and Cleveland and Oakland are so good, it might not be so easy for the Red Sox.

CORNISH: All right, I want to come back to Oakland now because they have the lowest payroll in baseball. They finished last in their division in the past three years. And yet right now, they're the hottest - one of the hottest teams anyway in baseball. How are they doing it?

KERI: They really have done a great job of exploiting market inefficiencies. It used to be that "Moneyball" was about on-base percentage, and now it's about home run hitting oddly. They have the second most home runs in the American League. And they've done it by identifying a lot of players who hit a bunch of fly balls. They did it before the curve so that when we learned, hey, the baseball's juiced, which is a recent revelation, it turned out Oakland already had the roster to take advantage of that. Those home runs, combined with a devastating bullpen and the best defense in the entire American League, have enabled the A's to overcome what's been the lowest payroll in all of baseball.

CORNISH: All right, so you have the American League, where they have these like big bad teams - right? - you know, four best records in baseball. That's like all in one league. And then meanwhile, the National League has, you know, people who are pretty good. But who's going to emerge from this group that can really challenge the American League champ in the World Series?

KERI: It's an open question because the team with the best record in the entire league right now, the Cubs, has an outside chance of missing the postseason. They haven't actually even clinched yet oddly because they're being chased down by the Milwaukee Brewers. Both of those teams have been really good. In the West, that's a half-a-game margin as well - the Dodgers and the Rockies.

The only team that's clinched right now is the Atlanta Braves. And unless you're the mom of one of the Atlanta Braves, you probably didn't think the Atlanta Braves were going to make the postseason this year. This is a big surprise. They came out of nowhere - bunch of young guys, including a guy named Ronald Acuna Jr. who's only 20 years old. He's going win the Rookie of the Year most likely. So it really is a dogfight.

It's not even just five teams that we're talking about because five make the postseason Pro league. It's really six because we know Atlanta's in. And then you've got Cubs, Brewers, Dodgers, Rockies. And the St. Louis Cardinals have a shot at the postseason too. You honestly could throw a dart at any of these six teams, and I could make a very strong case for you that any of those could win, and any of those could lose. It's as wide open as I can ever - literally ever remember the National League playoffs being.